1. Field of the Invention
The invention relates to an electrical supply circuit for a switch activating apparatus for moving an actuating element from a first switching position into a second switching position, a switch activating apparatus and a method for operating a switch activating apparatus.
EP 0 867 903 B1 and DE 103 09 679 B3 have disclosed switch activating apparatuses having an actuating element which can be moved to and fro in relation to a frame between a switch-off position and a switch-on position, in which apparatuses the actuating element is magnetically fixed in the switch-on position and mechanically fixed in the switch-off position.
In order to move the actuating element from the switch-off position into the switch-on position, a magnetic field produced by a coil is used. The electrical energy required for producing the magnetic field is stored in a closing capacitor.
In order to move the actuating element from the switch-on position into the switch-off position, essentially the resetting force of resetting springs is used. The resetting springs are tensioned during the movement of the actuating element from the switch-off position into the switch-on position, with the result that the energy required for moving the actuating element from the switch-on position into the switch-off position is stored substantially as mechanical energy in the springs. Only for releasing the magnetic fixing is it necessary to supply current to a release coil, which produces a magnetic field counteracting the fixing magnetic field. As soon as the fixing has been canceled and the switching operation of the resetting springs is driven, it is no longer necessary for there to be a current flow through the release coil. The electrical energy for the release coil is stored in an isolating capacitor, whose capacitance is markedly lower than that of the closing capacitor.
If the actuating element is now first guided from the switch-on position into the switch-off position and thereupon into the switch-on position again, the isolating capacitor first and thereupon also the closing capacitor are discharged. If thereupon the actuating element is again moved into the switch-off position, first the isolating capacitor needs to be recharged by means of an external charging unit, which may require a considerable amount of time. A rapid OCO (Open-Close-Open or switch-off-switch-on-switch-off) switching sequence can therefore not be ensured.
Other switch activating apparatuses known in the prior art have in particular isolating capacitors, whose capacitance can take up a multiple of the charge required for moving the actuating element from the switch-on position into the switch-off position. Although an OCO switching sequence is therefore possible without any intermediate charging by means of an external charging unit, against this other disadvantages need to be accepted with these control circuits. Since the capacitor is not completely discharged when the release coil is switched, the circuit comprising the capacitor and the coil needs to be interrupted at a suitable time, which makes it necessary to connect an inductive current. Furthermore, the voltage of the capacitor needs to be monitored in order to decide whether the remaining charge is still sufficient for operating the release coil.
Finally, it is also known from the prior art in the case of switch activating apparatuses as have been described at the outset to provide two isolating capacitors for the purpose of moving the actuating element from the switch-on position into the switch-off position, one of the two isolating capacitors being completely discharged in the case of each isolation in an OCO switching sequence.